Fig. 77.—The Dolly Varden Trout, Salvelinus malma (Walbaum). Lake Pend d'Oreille, Idaho. (After Evermann.)
In Alaska the Dolly Varden, locally known as salmon-trout, is very destructive to the eggs of the salmon, and countless numbers are taken in the salmon-nets of Alaska and thrown away as useless by the canners. In every coastwise stream of Alaska the water fairly "boils" with these trout. They are, however, not found in the Yukon. In northern Japan occurs Salvelinus pluvius, the iwana, a species very similar to the Dolly Varden, but not so large or so brightly colored. In the Kurile region and Kamchatka is another large charr, Salvelinus kundscha, with the spots large and cream-color instead of crimson.
Fig. 78.—Great Lake Trout, Cristivomer namaycush (Walbaum). Lake Michigan.
Cristivomer, the Great Lake Trout.—Allied to the true charrs, but now placed by us in a different genus, Cristivomer, is the Great Lake trout, otherwise known as Mackinaw trout, longe, or togue (Cristivomer namaycush). Technically this fish differs from the true charrs in having on its vomer a raised crest behind the chevron and free from the shaft. This crest is armed with strong teeth. There are also large hooked teeth on the hyoid bone, and the teeth generally are proportionately stronger than in most of the other species. The Great Lake trout is grayish in color, light or dark according to its surroundings; and the body is covered with round paler spots, which are gray instead of red. The dorsal and caudal fins are marked with darker reticulations, somewhat as in the brook-trout. This noble species is found in all the larger lakes from New England and New York to Wisconsin, Montana, the Mackenzie River, and in all the lakes tributary to the Yukon in Alaska. We have taken examples from Lake Bennett, Lake Tagish, Summit Lake (White Pass), and have seen specimens from Lake La Hache in British Columbia. It reaches a much larger size than any Salvelinus, specimens of from fifteen to twenty pounds weight being not uncommon, while it occasionally attains a weight of fifty to eighty pounds. As a food-fish it ranks high, although it may be regarded as somewhat inferior to the brook-trout or the whitefish. Compared with other salmonoids, the Great Lake trout is a sluggish, heavy, and ravenous fish. It has been known to eat raw potato, liver, and corn-cobs,—refuse thrown from passing steamers. According to Herbert, "a coarse, heavy, stiff rod, and a powerful oiled hempen or flaxen line, on a winch, with a heavy sinker; a cod-hook, baited with any kind of flesh, fish, or fowl,—is the most successful, if not the most orthodox or scientific, mode of capturing him. His great size and immense strength alone give him value as a fish of game; but when hooked he pulls strongly and fights hard, though he is a boring, deep fighter, and seldom if ever leaps out of the water, like the true salmon or brook-trout."
In the depths of Lake Superior is a variety of the Great Lake trout known as the Siscowet (Cristivomer namaycush siskawitz), remarkable for its extraordinary fatness of flesh. The cause of this difference lies probably in some peculiarity of food as yet unascertained.
The Ayu, or Sweetfish.—The ayu, or sweetfish, of Japan, Plecoglossus altivelis, resembles a small trout in form, habits, and scaling. Its teeth are, however, totally different, being arranged on serrated plates on the sides of the jaws, and the tongue marked with similar folds. The ayu abounds in all clear streams of Japan and Formosa. It runs up from the sea like a salmon. It reaches the length of about a foot. The flesh is very fine and delicate, scarcely surpassed by that of any other fish whatsoever. It should be introduced into clear short streams throughout the temperate zones.
Fig. 79.—Ayu, or Japanese Samlet, Plecoglossus altivelis Schlegel. Tamagawa, Tokyo, Japan.
In the river at Gifu in Japan and in some other streams the ayu is fished for on a large scale by means of tamed cormorants. This is usually done from boats in the night by the light of torches.